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In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 10Journal Name RSC Advances Dynamic Article Links ► Cite this: DOI: 10.1039/c0xx00000x www.rsc.org/xxxxxx ARTICLE TYPE Reverse Iodine Transfer Polymerization (RITP) of Chloroprene Jia Hui, Yan Shi,* Tao Li, Jie Wu and Zhifeng Fu Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX DOI: 10.1039/b000000x 5 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China E-mail: [email protected] Fax: +86-010-64423811; Tel: +86-010-64416783 10 Reversible-deactivation radical polymerization (RDRP) of chloroprene (2-chloro-1,3-butadiene, CP) using reverse iodine transfer polymerization (RITP) has been demonstrated for the first time. Reverse iodine transfer polymerizations of CP were studied in benzene at 50 oC using 2,2'-azobis(isoheptonitrile) (ABVN) as radical initiator, where a molar ratio ABVN/I 2=1.7 was used. The process efficiently controls 15 the molar mass (characterized by size exclusion chromatography, SEC) and the structure of the polymer Manuscript 1 -1 (confirmed by H NMR spectra). For example, polychloroprene (PCP) samples of Mn,SEC = 4900 g mol -1 -1 - and Mw/M n = 1.73 (M n,th = 4800 g mol ), Mn,SEC = 7300 g mol and Mw/M n = 1.89 (M n,th = 7300 g mol 1 -1 -1 ), and M n,SEC = 9000 g mol and Mw/M n = 1.86 (M n,th = 9300 g mol ) were successfully obtained. Furthermore, the influence of solvent, initiator and temperature were studied. Last, the controlled nature 20 of the polymer was confirmed by the preparation of polychloroprene-b-polystyrene (PCP-b-PSt) and polychloroprene-b-poly(methyl methacrylate) (PCP-b-PMMA) diblock copolymers. Regarding the synthetic aspect, CR synthesizes via Introduction uncontrolled fashion with sulfur or mercaptans used as chain- Accepted 50 terminating agents in industrial field. There has been limited Over the last few years reversible-deactivation radical 1 success of the reversible-deactivation radical polymerization polymerization (RDRP) has led to interesting academic and behavior of CP despite the fact that it can be polymerized via a 25 industrial researches due to the ability to synthesize well-defined radical mechanism. This is partially due to the high reactivity of polymers and complex macromolecular architectures such as the CP monomer because of a chlorine substituent. To date, CP block, comb and star copolymers. To date, the most important 55 was only involved in a few examples of RDRP such as NMP, ITP RDRP techniques are nitroxide mediated polymerization and RAFT polymerization. However, NMP, ITP and RAFT (NMP), 2,3 atom transfer radical polymerization (ATRP), 4,5 iodine 6-9 polymerization suffer drawbacks of different kinds. NMP 30 transfer polymerization (ITP), and reversible addition o 18 10,11 requires relatively high reaction temperature (100 C). The fragmentation chain transfer (RAFT) polymerization. RAFT polymerization of CP was previously demonstrated by our Chloroprene (2-chloro-1,3-butadiene; CP) is a very important 19 20 60 group and by others workers. The drawback of the RAFT Advances monomer, which utilized primarily in the manufacture of method is high cost, difficult availability of RAFT agents. In ITP chloroprene rubber (polychloroprene, CR). CR is one of the most examples, the emulsion polymerization of CP is carried out using 35 commonly used synthetic rubbers in the rubber industries. CR has 21 iodoform (CHI 3) as the chain transfer agent. Iodoform presents been widely used in industrial rubbers, contact adhesives, wires, the disadvantage of being unstable and difficult to handle, which and various other numerous applications due to its many 65 is known to be one of the main problem in ITP process. It is RSC fascinating properties. To meet these emerging needs and for new widely known that iodine is a strong radical scavenger and material development for more demanding applications, inhibitor of radical polymerizations. The recent discovery of the 40 improvements of CR products are very desirable. The physical reverse iodine transfer polymerization (RITP) process is a modification of CR is frequently carried out through polymer 22 breakthrough in the field of radical polymerization. Lacroix- blends.12-14 Graft copolymerization is also an important method in 15 70 Desmazes and co-workers showed that the iodinated chain modifying chemical and physical properties of CR. As a matter transfer agents is in situ synthesized based on the direct reaction of fact, the choice of the RDRP techniques, which open the door of the initiator with I2, avoiding the presynthesis and storage of 45 to synthesize block, comb and star copolymers, becomes of great the unstable alkyl iodide in RITP mechanism. The consumption relevance via the introduction of specific functionalities on of monomer in this step is low and it is called the inhibition polymer backbones or chain ends.16,17 75 period. Once all molecular iodine is consumed, the This journal is © The Royal Society of Chemistry [year] [journal] , [year], [vol] , 00–00 | 1 RSC Advances Page 2 of 10 polymerization period takes place (Scheme 1). This technique has by size exclusion chromatography (SEC), 1H NMR to determine been sucessfully used to polymerize styrenic monomers the molar masses and their composition, respectively. The (styrene), 23-25 acrylic monomers (methyl acrylate, 22 methyl monomer conversions were calculated by gravimetric analysis. 26,27 22,28 methacrylate, n-butyl acrylate …) in homogeneous and 50 Synthesis and characterization of a macro-chain transfer 28-31 -1 5 heterogeneous polymerizations. However, to the best of our agent PCP-I with M n,targeted = 2900 g mol ([CP]/[ABVN]/[I 2] knowledge, no chloroprene has been polymerized under RITP. = 60/1.7/1) CP (10 g, 1.13×10 -1 mol), ABVN (0.7948 g, 3.20×10 -3 mol), iodine (0.4781 g, 1.88×10 -3 mol), and benzene (15 mL) were 55 introduced in a 50 mL round bottomed flask equipped with a magnetic bar. The reaction medium was purged with argon for 10 min at 0 oC to remove oxygen. Five freeze-thaw-pump cycles were completed and the flask was placed in an oil bath at 50 oC. The polymerization was conducted in the dark, with magnetic 60 stirring and under argon atmosphere. The reaction was stopped when the monomer conversion reached 100% for 18 h. Chain extension of PCP In a typical procedure for the chain extension reaction with CP, in Scheme 1 Simplified reaction scheme for the mechanism of the Schlenk flask containing the crude sample of the above reverse iodine transfer polymerization (RITP). 65 mentioned PCP-I were added 45.8 g (517 mmol) of CP and 10 In this article, RITP of chloroprene is reported for the first 0.1427 g (0.57 mmol) of ABVN ([ABVN]/[PCP-I] = 0.17). Five time. We examine the effect of solvent and temperature on the freeze-thaw-pump cycles were carried out, and then the flask was o degree of control achieved in RITP of CP. As an extension of this placed in an oil bath at 50 C. The polymerization was conducted Manuscript investigation, we present the the possibility to synthesize for 25 h in the dark, with magnetic stirring and under argon polychloroprene-block -polystyrene (PCP-b-PSt) and 70 atmosphere. 15 polychloroprene-block -poly(methyl methacrylate) (PCP-b- Synthesis of block copolymers PMMA) diblock copolymers by sequential RITP of chloroprene followed by ITP of St and MMA, respectively. Thus, one can Block copolymers were prepared by the macro-chain transfer obtain adhesives and blend compatibilizers, or thermoplastic agent (macro-CTA) method. elastomers, etc. Synthesis of PCP-b-PSt diblock copolymer 75 In a typical procedure for block copolymerization, in the Schlenk 20 Experimental Section flask containing the crude sample of the above mentioned PCP-I Accepted Materials were added 37.2 g (357 mmol) of styrene and 0.1955 g (1.19 Chloroprene was provided by China Blue Star Shanxi Synthetic mmol) of AIBN ([AIBN]/[PCP-I] = 0.3). Five freeze-thaw-pump cycles were carried out, and then the flask was placed in an oil Rubber Group Co., Ltd. (Datong, China) and used without further o purification. Styrene (St) and methyl methacrylate (MMA) (99%, 80 bath at 65 C. The polymerization was conducted in the dark, with magnetic stirring and under argon atmosphere to prepare a 25 Tianjin fuchen chemical plant) were distilled under reduced pressure and stored in a freezer before use. Benzoyl peroxide PCP-b-PSt copolymer. The tube was removed from the oil bath (BPO) was dissolved in chloroform and precipitated into cooled after a given time interval and the reaction mixture was ethanol; the crystals were filtered off and dried. 2,2′- immediately immersed in a water/ice bath to stop the reaction.